In recent years, as one of methods for miniaturizing a semiconductor device and for achieving high performances thereof, a packaging technique has been developed, in which semiconductor substrates each made of a single crystal silicon (hereinafter, referred to as silicon substrate) are laminated so that the silicon substrates are electrically connected to each other by using fine electrode wires.
As a recently-focused technique of the above-described packaging techniques, there is a method in which integrated circuits formed on a plurality of silicon substrates are electrically connected to each other by using fine electrodes each referred to as bump electrode which connects silicon substrates with each other or electrodes each referred to as silicon through electrode (Through Silicon Via) which penetrates through a silicon substrate.
In the case of a semiconductor device to which the above-described technique is adopted, the connection reliability of the bump electrodes which connect the silicon substrates with each other deteriorates due to a stress caused by heat and impacts applied to the silicon substrates. For this reason, a technique for ensuring the connection reliability of the bump electrodes in which the bump electrodes are protected by sealing the periphery of the bump electrodes with an insulator such as a resin is essential.
One of methods for sealing the periphery of the bump electrodes with the resin is a pre-coating method. This is a method for electrically connecting the bump electrodes with each other by, prior to a step for bonding two silicon substrates (for example, silicon wafers) having bump electrodes formed thereon with each other, coating each silicon substrate with a thermosetting resin represented by an epoxy resin, and then, thermally compression-bonding the two silicon substrates with each other.
However, in the case of the above-described pre-coating system for connecting the bump electrodes with each other by coating the silicon substrates having the bump electrodes formed thereon with the resin, and then, thermally compression-bonding the silicon substrates with each other, the resin adhered onto a surface of the connection of the bump electrodes sometimes enter a space between the bump electrodes upon the thermal compression-bonding. This entering causes a high contact resistance between the bump electrodes, and besides, a non-contact state between the bump electrodes or others, which result in a problem of a reduction of the connection reliability of the bump electrodes.
Accordingly, in order to eliminate such a failure as the entering of the resin into the space of the surface of the connection between the bump electrodes, some methods in which flattened bump electrodes and a resin are simultaneously joined with each other so as to simultaneously perform connection of the bump electrodes with each other and connection of the resins with each other have been proposed.
For example, the following Patent Document 1 (Specification of U.S. Patent Application Laid-Open Publication No. 2007/0207592) discloses a method of forming a resin portion having an opening portion in a silicon substrate having an LSI formed thereon, and then, burying a bump electrode material into the opening portion of the resin, performing polishing so that there is no step between the resin and an upper surface of the bump electrode to be flattened, similarly forming the bump electrode and the resin in another silicon substrate having an LSI formed thereon, and bonding the resins formed on the two silicon substrates with each other and the electrodes thereon with each other by thermal compression bonding.
Patent Document 2 (Japanese Patent Application Laid-Open Publication No. H07-014982) discloses the following step as a method for bonding two substrates with each other. First, a protective insulating film (12) on a quartz substrate (30) side is opened, metal films (65 and 66) mainly made of Al are buried in the opening portion, and they are flattened on the same level as a surface of the protective insulating film (12). Further, a thick polycrystalline Si film (24) is deposited on a semiconductor integrated circuit device formed on another single crystal Si substrate (11), and polishing a surface of the film to be flattened, and then, forming an adhesive layer (23) made of a fluorine-based resin on the surface thereof. Next, an opening portion reaching the semiconductor integrated circuit device is formed in the adhesive layer (23), and then, an insulting treatment is performed onto an opening portion side wall, metal films (67 and 68) mainly made of Al are buried into the opening portion and are flattened. Then, these substrates are bonded with each other (see FIGS. 25 and 26).